Method for making nitrogenous and complex fertilizers in highly homogenized spherical granule form starting from urea formaldehyde liquid resins and the fertilizer made thereby

ABSTRACT

The present invention relates to a method for making nitrogenous and complex fertilizers, in granule form, suitable for slowly releasing nitrogen, comprising the steps of preparing an aqueous urea/formaldehyde dispersion with a molar ratio from 0.8:1 to 2:1, adding an aqueous catalyzer solution in a weight ratio from 0.1 to 4%, controlling the pH of the aqueous dispersion to hold it within a range from 4.0 to 7.0, and supplying the aqueous dispersion to a recirculating granulating device, as a growth seed.

BACKGROUND OF THE INNVENTION

[0001] The present invention relates to a method for making fertilizers,optionally with microelements, in a spherical granule form having a highgranulometric homogeneity, starting from urea-formaldehyde resins inliquid form, and to the fertilizers made thereby.

[0002] Actually, also the fertilizers made by the inventive methodconstitute an integrating part of the invention.

[0003] As is known, urea-formaldehyde (UF) resins in solid form and oflow molecular weight, are fertilizers adapted to slowly releasenitrogen, both due to a high contents of said nitrogen (>36%), and totheir capability of gradually continuously releasing nitrogen for adirect absorption by plants and the like.

[0004] This latter feature is a very important both from an economicaland environmental standpoint.

[0005] Available fertilizers are compounds having a very high watersolubility, and accordingly these compounds can be easily flushed orwashed away by rain and irrigation waters.

[0006] In turn, this flushed away material can. contaminate waters andground water tables and moreover, since the flushed away material cannotaid the plant growth, it must be supplemented by new fertilizercompounds.

[0007] The efficiency of UF resins based nitrogenous fertilizers,including UF resins in solid form, is measured by the so-called“Activity Index” (AI) parameter, which is related to the respectiveamounts of hot water (HWIN) and cold water (CWIN) insoluble resins, andis bound to the nitrogen releasing rate as follows:

AI=100·(1−HWIN/CWIN).

[0008] Small values of the above mentioned parameter AI are indicativeof a slower releasing, whereas high values are indicative of a quickerreleasing.

[0009] A standard nitrogenous fertilizer would have an AI value from 40%to 60%.

[0010] Prior urea-formaldehyde condensation products, containing lowwater solubility methylene-urea, have a nitrogen amount contents whichcan be released to plants within a long time period.

[0011] In turn, UF resins, used as a nitrogenous fertilizer, have acomparatively high value, both due to their high nitrogen contents, andtheir nitrogen releasing characteristics, both in cold and hot water.

[0012] The water soluble longer chains, on the other hand, can behydrolized much more slowly than shorter chains.

[0013] The releasing efficiency abruptly decreases for oligomersincluding a urea amount larger than 5 units (tetramethylenepentaurea)and, at such an amount, they become nearly unattachable by the soilmicroorganisms.

[0014] Many commercially available fertilizers based on solid UF resinshave a high hot water insolubility nitrogen rate, (HWIN), thereby thisnitrogen, accordingly, would be practically unavailable for plants.

[0015] Thus, for reducing the hot water insoluble nitrogen amount, whileholding the cold water insoluble fraction, thereof nearly unaltered, twomethods have been conventionally used.

[0016] The first of these methods provides to add to theurea/formaldehyde mixture a further urea amount.

[0017] By this method, however, the excess free urea causes an increaseof the fertilizer phytotoxicity.

[0018] The second method, in turn, provides to add ammonia in the formof ammonium salts in order to favour a formation of low molecular weightcondensation products, in general not higher than trimers(dimethylenetriurea).

[0019] The condensation reaction of urea and formaldehyde is usuallycarried out by two stages:

[0020] 1) in the first stage, urea and formaldehyde, in suitable ratiosfrom 1.3 to 1.2 and at a pH from 7 to 10, are mixed at environment orroom temperature, thereby favoring formation of methylolurea.

[0021] 2) in the second stage, the mixture is acidified and heated (at apH from 4.5 to 6.0 and at a temperature from 80 to 110° C.), therebyproviding a UF resin.

[0022] The reaction can also be carried out in a single stage, byacidifying at low temperature (20÷40° C.) for a long time; however, sucha method would provide a product very rich in free urea, with consequentphytotoxicity problems as the resin is used as a fertilizer.

[0023] An alternative method could comprise a use of an alcohol as areaction solvent (either methyl or ethyl alcohol).

[0024] The urea-formaldehyde condensation reaction is always carried outby acidifying methylolurea formed in a basic environment or medium, thetemperature being, in such a case, controlled by boiling the solventoff, since said solvent would operate as a thermal “flywheel”.

[0025] More specifically, the condensing/drying reaction can be directlycarried out in a granulating device, for example of a fluid bed type, orin a spraying-drying tower or column or, alternatively, in a CFSRreactor, to exit therefrom as a suspension to be supplied to aturbo-dryer or other like apparatus.

[0026] Alternatively, the liquid form can be adsorbed on inert inorganicmaterials (vermiculite and clays in general).

[0027] For making fertilizers in grain form starting from a foamedresin, the condensing reaction is carried out by acidifying in thepresence of surface active materials (0.05÷2%) and/or air in a reactorincluding a suitable stirring device.

SUMMARY OF THE INVENTION

[0028] The aim of the present invention is to improve the abovedisclosed results, by providing a method for making nitrogenous andcomplex fertilizers, designed for slowly releasing nitrogen, in granuleform, thereby providing a product of high granulometric homogeneity andsusceptible to be easily applied by conventional applying means forevenly distributing granular or granule form fertilizers.

[0029] In addition to nitrogen, The above mentioned products can alsocontain primary fertilizer elements (K, P), secondary fertilizerelements (Mg, Ca, S) and micro-elements (B, Fe, Zn, Mn, Cu, Mo).

[0030] Within the scope of the above mentioned aim, a main object of thepresent invention is to provide such a method allowing to easily andaccurately control production parameters such as: catalyzer contents,drying air temperature, solid phase/liquid phase ratio inside thegranulating device, as well as the holding time of the made compound insaid granulating device.

[0031] A further object of the present invention is to provide such amethod which is operatively very reliable and safe.

[0032] Yet another object of the present invention is to provide amethod for making nitrogenous and complex fertilizers, for slowlyreleasing nitrogen, in granule form, which can be easily carried out byusing easily commercially available elements and apparatus.

[0033] Yet another object of the present invention is to provide such amethod which is very competitive from a mere economic standpoint.

[0034] According to one aspect of the present invention, the abovementioned aim and objects, as well as yet other objects, which willbecome more apparent hereinafter, are achieved by a method for makingnitrogenous and complex fertilizers, for slowly releasing nitrogen, ingranule form, characterized in that said method comprises the steps ofpreparing an aqueous urea-formaldehyde dispersion with a molarurea/formaldehyde ratio from 0.8:1 to 2:1, adding to said dispersion anaqueous catalyzer solution in a weight ratio from 0.1 to 4%, controllinga pH of said dispersion to hold said pH within a range from 4.0 to 7.0,and supplying the mixture to a granulating device, said granulatingdevice including recycling means for recycling the product as a growthseed.

[0035] Further characteristics and advantages of the present inventionwill become more apparent hereinafter from the following detaileddisclosure of a preferred, though not exclusive, embodiment of a methodfor making nitrogenous and complex fertilizers, for slowly releasingnitrogen, in granule form, which is illustrated, by way of a merelyindicative but not limitative example, in the accompanying drawings.

[0036] More specifically, the method according to the present inventionis generally based on a reactive drying, to, be performed in agranulating device, of liquid form urea/formaldehyde resin, which issprayed on a solid support comprising uneven granule of small size,which granules can also be obtained by frantumating or crushing a amountof finished product.

[0037] The liquid form urea/formaldehyde resin, in a ready for usecondition, is stored in storing tanks near the processing system,likewise to the catalyzer tank.

[0038] From the storing tanks, the liquid resin is conveyed to a mixer,and then supplied to the granulator or granulating device.

[0039] In order to cause the granule-form urea/formaldehyde resin tosolidify water contained in the liquid resin is evaporated off, and thepolycondensation reaction is properly controlled.

[0040] In particular, the parameters controlling this process are: thecatalyzer contents, drying air temperature, solid phase/liquid phaseratio and holding time in said granulating device.

[0041] The growth favoring seed is conveyed through the granulatingdevice to be progressively enlarged size.

[0042] At the outlet of the granulating device, the granule compound isconveyed to a two net or mesh screen, where the granules are properlysieved out.

[0043] The first net of said granulating device is provided to removethe oversized product, which is frantumated to provide a portion of thegrowth seed.

[0044] The second net separates the desired granulometry material fromthe finer material which is recirculated.

[0045] All of the powder loaded air from the system is collected andconveyed to a filter.

[0046]FIG. 1 to 3 illustrate hystrogram graphs or diagrams related togranulometry measurements carried out in typical granulating tests, withan extrapolation of a theoretical curve, obtained by using the Gauss'function.

[0047] An examination of the hystogram diagrams would allow to statethat the granulating process herein claimed provides a very highgranulometric homogeneity product, which can be accordingly easilyapplied by conventional application means as those used for distributinggranule form fertilizers.

3. Agronomic Test

[0048] From a lot of practical actually performed test, it has beenfound that the made fertilizer is very useful because of itsspecifically designed structural and chemical properties.

[0049] The agronomic efficiency of the granule form UF fertilizer, hasbeen evaluated by manuring tests on maize, using, in addition to the UFfertilizer, other 2 comparing fertilizers, i.e.: Urea and Floranid(based on IBDU).

[0050] The distributed nitrogen amounts were: 300 Kg/ha (whichrepresents an optimum dose for maize), 225 Kg/ha (which represents anoptimum dose reduced by 25%) and 150 Kg/ha (which represents an optimumdose reduced by 50%).

[0051] The following Table 1 shows data related to the above mentionedtest, which have been calculated as a dry weight of the maize ear, inwaxy milky ripening conditions, with respect to a non manured sample.TABLE 1 Maize manuring test Effect of the interaction “manured type fornitrogen doses” Dry weight of the maize ear, in grams NYTROGEN DOSESManure form 0 Kg/ha 50 Kg/ha 225 Kg/ha 300 Kg/ha UREA / 153.0 167.3176.2 FLORANID (IBDU) / 165.4 177.6 180.0 SADEPAN 39.0.0 Granular /163.2 187.7 198.8 Non Manured SAMPLE 135.5 / / /

[0052] It should be apparent that the best results have been obtained by39-0-0 at 225 and 300 Kg/ha; at a small dose, the results can becompared, with the exception of that related to urea.

[0053] A second test has been performed to study the nutritional effecton sugar beets of the granule form UF fertilizer, once fully applied inseeding the culture, compared with a program based on Urea and AmmoniumNitrate, distributed by two distributing operations, i.e.: in apre-seeding operation, and a portion at the 6-leaf stage of the sugarbeets.

[0054] The distributed-nitrogen amounts are included in a 40 to 160Kg/ha nitrogen. TABLE 2 Effect of the manuring method on the a-Ncontents a-N Contents Meg/100 g Manuring method Pulp UREA + AMM.NITR.1.49 b SADEPAN 39.0.0 granular 1.16 a D.M.S. (P 0.05) 0.24

[0055] The results of Table 2 show that the inventive fertilizer alwaysprovided, independently from its application dose, a nitrogen contentsso-called “noxious” (i.e. an alpha-amine nitrogen present in extractionjuices inhibiting crystalization of sugar) less than that obtainedaccording to the manuring program based on conventional fertilizers.TABLE 3 Effects of the manuring method and nitrogen dose on the“alcalinity coefficient” of the juices. Nitrogen Dose (Kg/ha) Manuringmethod 0 40 80 120 160 Urea + 5.62 b 5.53 b 3.92 c 3.93 c Amm.Nitr. Nonmanured 6.25 a sample SADEPAN 39.0.0 Granular   6.55 ab   6.75 ab 5.51 b7.77 a

[0056] Table 3 shows data related to the technologic processingparameters of juices in the sugar making system: the so-calledalcalinity coefficient.

[0057] Juices having a high alcalinity coefficient are very useful,since, an alcalinity coefficient of low values, would involve a greaterconsume of crystalizing reagents (soda, limestone), and a great wear ofthe concentrating devices.

[0058] By using conventional manures, the alcalinity coefficient tendsto lower as the applied nitrogen dose increases, whereas, by using thegranule form UF fertilizer according to the present invention, this doesnot occur.

[0059] With respect to conventional urea based fertilizers available onthe agricultural market, the granule fertilizer according to the presentinvention, is characterized in that it comprises a coherent “slowlyreleased” nitrogen fraction.

[0060] Thus, due to this characteristic, better agronomic performance ofthis nutritional agent are obtained, as it would actually be necessaryfor a balanced plant growth, with a consequent less consume of thegranule compound, the agricultural yield being the same, and with aconsequent smaller loss due to bleaching and percolation from soil (abetter environmental impact, and a less or no contamination of the watertable).

[0061] Laboratory and field tests have demonstrated and assured a lessconsume of nitrogen, the agricultural yield being the same, and a greatpower saving, due to a less number of passages of the distributingmechanical equipment through the soil.

[0062] From the above mentioned data, it should be pointed out that the,granule UF form as claimed in the present application, is that offeringthe best agronomic yield.

4. EXAMPLES

[0063] The following examples are herein shown in order to illustratethe invention without limiting it.

[0064] The rough materials and chemical products used therein are asfollows:

[0065] Formaldehyde 43: an aqueous solution at 43% by weight offormaldehyde.

[0066] Formurea 70: a urea-formaldehyde precondensate having a molarratio, expressed as urea: formaldehyde, generally from 1:5.7 and 1:6.3and a theoretical dry residue, expressed as a percentual sum of urea andformaldehyde, generally from 69 to 71.

[0067] It is constituted by formaldehyde (˜53%) and urea (˜17%).

[0068] Formurea 80: a urea-formaldehyde precondensate. Having a molarratio of 1:4.95 and a theoretical dry residue of 80.

[0069] It is constituted by formaldehyde (57%) and urea (23%).

[0070] Urea in pearl or pellet form: an industrial use urea.

[0071] Water: deironed water, preferably also softened or sweetened.

[0072] Catalyzers: sulphuric acid at 10%, sulphamic acid 50%, ammoniumnitrate 50%, ammonium sulphate 30%, ammonium chloride 20%, monoammoniumphosphate 25%, ammonium acetate 33%, formic acid 20%, hydrochloric acid17%, nitric acid 30%, phosphoric acid 55%, acetic acid 55% and ammoniumformate 30%.

[0073] Alkalinizing agents: sodium hydroxide 30%, potassium hydroxide25%, triethanolamine 50%, monoethanolamine 50%, diethanolamine 50%,ammonia 20÷50%, sodium and potassium carbonates, solidhesamethylentetramine or 40% hesamethylentetramine solution, calciumhydroxide, magnesium hydroxide, sodium tetraborate.

[0074] Hereinbelow are listed nutritional element containing chemicalproducts, which can be identified as macro, meso, and microelements,which can be added to the liquid-form UF compound:

[0075] Hydrated Sodium Octoborate or hydrated Sodium Tetraborate orBoron (ethanolamina) as sources of Boron.

[0076] Zinc Oxide or Zinc Sulphate or Zinc—EDTA as sources of Zinc.

[0077] Iron Sulphate or Iron—EDTA or Iron—EDDHA or Iron—EDDHSA or IronDTPA as sources of Iron (II).

[0078] Manganese Sulphate or Manganese—EDTA as sources of Manganese.

[0079] Copper Sulphate or Copper Chloride or Copper Oxide or Copper—EDTAas sources of Copper.

[0080] Ammonium Molybdate, Sodium or Potassium Molybdate, as sources ofMolybdene.

[0081] Magnesium Sulphate or Magnesium Hydroxide, or Magnesium Nitrateor Magnesium Chloride as sources of Magnesium.

[0082] Calcium Nitrate or Calcium Chloride or Calcium Sulphate assources of Calcium.

[0083] Magnesium Sulphate or Manganese or Potassium Sulphate or Iron orZinc or Calcium Sulphate as sources of Sulphur-SO.

[0084] Potassium sulphate or Potassium Chloride or Potassium Nitrate orMonopotassium Phosphate or Di-potassium Phosphate as sources ofPotassium.

[0085] Monopotassium Phosphate or Di-potassium Phosphate or PhosphoricAcid or Polyphosphoric Acids or Ammonium Polyphosphate as sources ofPhosphate.

[0086] Ammonium Nitrate or Sodium Nitrate or Potassium Nitrate orMagnesium Nitrate or Calcium Nitrate as sources of Nitric Nitrogen.

[0087] Ammonium Nitrate or Ammonium Sulphate or Ammonium Phosphate orAmmonium Sulphonitrate as sources of Ammoniacal Nitrogen.

[0088] The hereinbelow disclosed Examples, indicated by odd numbers 1,3, 5, 7, 9, 11, 13, 15, 17, 19, will disclose e preparing of liquid formUF resin and are all related to 1000 Kg of finished product.

[0089] For each of the above mentioned examples, an Example of thedisclosure of the consequently made granular form UF product willfollow:

[0090] The latter have been indicated by even numbers from 2 to 20.

Example No. 1 Preparing the Liquid form UF Resin

[0091] Into a steel reactor having a size variable from 10,000 to 60,000litres, including a stirring system and a heating and cooling system,are loaded, under stirring and at atmospheric pressure and roomtemperature, the following rough materials. 80% Formurea  Kg 350.9 WaterKg 49.8 Urea Kg 79.3

[0092] (molar ratio CH₄N₂O/CH₂O=1/2.5).

[0093] The mixture is heated to 90° C., and 0.5 Kg 20% Formic Acid areadded to provide a pH from 5.0 to 5.5.

[0094] The reaction, as monitored at even time periods by dynamicviscosity measurements at 20° C., is stopped at 1,500 mPas, by adding0.5 Kg 30% Soda.

[0095] After stopping the reaction, neutrality is achieved.

[0096] There are moreover loaded:

[0097] 106.7 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.5), with temperaturebeing held at 70° C. for 30 minutes.

[0098] There are then added:

[0099] 145.7 Kg Water

[0100] 266.6 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.75).

[0101] The mixture is held at 45° C. for 60 minutes, then it is cooledand supplied to the storing tank.

[0102] The finished product contains 24.8% in total of nitrogen.

Example No. 2 UF Resin Granulating Test

[0103] The liquid material of Example 1 (having a pH=7.5÷8.0 and aviscosity at 20° C.=350÷400 mPas) is supplied to a 100 liter mixer heldunder constant stirring and heated to 50÷60° C., thereby lowering theviscosity to 60÷80 mPas.

[0104] By a displacement type of pump, the mixture is then supplied tothe granulating device; a static mixer arranged on the pumping lineprovides a mixing with the catalyzer (Ammonium Sulphate at 30%, in arate of 1.66% by weight on the liquid material): this causes a loweringof the mixture pH to 5.6÷5.8.

[0105] At the outlet of the granulating device, the granules areconveyed through a two-net sieve: the fraction from 2.0 to 4.0 mmconstituting the finished product.

[0106] Characteristics of the finished product: Shape White sphericalgranules; Granulometry 20.0 ÷ 2.5 mm; Total Nitrogen 38.0% minimum; Hotwater soluble nitrogen 23% minimum; Granule hardness 1.5 ÷ 2.0 Kg;Friability 1% maximum; End moisture 1.5 maximum; Apparent density ˜0.75g/cm; Activity index 20 ÷ 25%; Ureic nitrogen 4% maximum; Heatingpacking it is not packed after 1 month at 70° C. in a thermo- statizedstove; Compression packingr it is not packed after 1 Month under a loadof 200 g/sm.

Example 3 Preparing the Liquid form UP Resin

[0107] Into a steel reactor having a size variable from 10,000 to 60,000including a stirring system and a heating and cooling system, areloaded, under stirring, at atmospheric pressure and room temperature,the following raw materials. Formurea 70%  Kg 434.0 Water Kg 76.2 UreaKg 79.5

[0108] (molar ratio CH₄N₂O/CH₂O=1/3.0)

[0109] The mixture is heated to 95° C. and 0.4 Kg 30% Ammonium Sulphateare added: the pH is lowered to 5.5÷6.0.

[0110] The mixture is held at 95° C. for 30 minutes, without controllingits viscosity.

[0111] The reaction is partially stopped by adding 0.1 Kg 20% SodiumCarbonate.

[0112] After this adding step, the pH achieves a value of 6.0÷6.2 andthe reaction is continued by adding:

[0113] 76.7 Kg urea (molar ratio CH₄N₂O/CH₂O=1/2.0).

[0114] The temperature falls to 80° C., but it must be recovered to 95°C.: in this step the reaction is stopped as its viscosity achieves 1,200mPas.

[0115] A full stopping of the reaction is made by adding 0.2 Kg 30%Soda.

[0116] After stopping the reaction, the pH of the mixture is near toneutrality.

[0117] Then are loaded:

[0118] 82.8 Kg Water

[0119] 247.7 Kg Urea (and molar ratio CH₄N₂O/CH₂O=1/0.96)

[0120] 2.4 Kg hydrated Sodium Octoborate

[0121] The mixture is at 40° C. for 60 minutes, then it is cooled andsupplied to the storing tank.

[0122] The finished product contains in total 22.3% Nitrogen and 0.05Boron.

Example No. 4 UF Resin Granulating Test

[0123] The liquid of Example 3 (having a pH 8.5÷9.0 and a viscosity at20=550÷650 mPas) together with a water soluble yellow coloring or dyeingmaterial (few ppm's are sufficient) is conveyed to a 100 liter mixer,held under constant stirring and heated to 55÷65° C., thereby causingits viscosity to be lowered to 80÷100 mPas.

[0124] By a displacement pump, the mixture is then supplied to thegranulating device; a static mixer arranged on the pumping line assureits mixing with the catalyzer (20% Formic Acid in a rate of 2.5% byweight on the liquid amount) and the pH of the mixture is lowered to5.8÷6.0.

[0125] At the outlet of the granulating device, the granules areconveyed through a two-net sieve: the fraction from 1.5 to 3.0 mm formsthe finished product.

[0126] Characteristics of the finished product: Shape Yellow sphericalgranules; Granulometry 1.5 ÷ 2.0 mm; Total Nitrogen 36.0% minimum;Microelements 0.06% Boron Hot water soluble nitrogen 22% minimum;Granule hardness 1.0 ÷ 1.5 Kg; Friability 1% maximum; End moisture 2.0maximum; Apparent density ˜0.75 g/cm³; Activity index 30 ÷ 35%; Ureicnitrogen 3% maximum; Packing by heating: it is not packed after 1 monthat 70° C. in a thermo- statized stove; Compression packing it is notpacked after 1 month under a load of 200 g/cm².

Example 5 Preparing the Liquid form UF Resin

[0127] Into a steel reactor having a size variable from 10,000 to 60,000liters including a stirring system and a heating and cooling system, areloaded, under stirring, at atmospheric pressure and room temperature,the following raw materials: 43% Formaldehyde Kg 418.6 30% Soda Kg 0.25 Urea Kg 180.0

[0128] The mixture is heated to 100° C. and 0.6 Kg 20% Formic Acid areadded, to cause the pH to be lowered to 4.5÷4.8.

[0129] The reaction, monitored at even time periods by dynamic viscositymeasurements at 20° C., is stopped by adding 0.6 Kg 30% Soda, as aviscosity of 150 mPas is achieved.

[0130] After stopping the reaction, the neutrality is achieved.

[0131] Then are loaded:

[0132] 4.15 Kg Water

[0133] 120.0 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.2) and the temperatureis held at 60° C. for 40 minutes, and then are added:

[0134] 253.8 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.65)

[0135] 22.0 Kg Zinc-EDTA.

[0136] The mixture is held at 60° C. for 60 minutes, then it is cooledand supplied to the storing tank.

[0137] The finished product contains 25.8% in total nitrogen and 0.4%Zinc.

Example No. 6 UF Resin Granulating Test

[0138] The liquid of Example 5 (having a pH=7.0 and a viscosity at 20°C.=850÷950 mPas), together with a water soluble sky-blue coloringmaterial (few ppm's are sufficient) are supplied to a 100 liter mixer,held under a constant stirring and heated to 50÷60° C., thereby causingthe mixture viscosity to be lowered to 130÷150 mPas.

[0139] By a displacement type of pump, the mixture is supplied to thegranulating device; a static mixer arranged on the pumping line providesa mixing with the catalyzer (20% Formic Acid in a rate of 1.5% by weightbased on the liquid) and the pH of the mixture is lowered to 5.8÷6.0.

[0140] At the outlet of the granulating device, the granules areconveyed through a two-net sieve: the fraction from 2.0 to 4.0 mmconstitutes the finished product.

[0141] Characteristics of the finished product: Shape Sky-blue sphericalgranules; Granulometry 20.0 ÷ 2.5 mm; Total Nitrogen 39.0% minimum;Microelements 0.6% Zinc Hot water soluble nitrogen 26% minimum; Granulehardness 2.5 ÷ 3.0 Kg; Friability 0.5% maximum; End moisture 1% maximum;Apparent density ˜0.80 g/cm; Activity index 40 ÷ 45%; Ureic nitrogen 5%maximum; Packing by heating it is not packed after 1 month at 70° C. ina thermo- statized stove; Compression packing it is not packed after 1Month under a load of 200 g/cm².

Example 7 Preparing the Liquid form UF Resin

[0142] Into a steel reactor having a size variable from 10,000 to 60,000liters, including a stirring system and a heating and cooling system,are loaded, under stirring, at atmospheric pressure and roomtemperature, the following raw materials: 70% Formurea Kg 434.0 Water Kg47.2  Urea Kg 110.2

[0143] The mixture is heated to 90° C. and 0.4 Kg 20% formic acid areadded to lower the mixture pH to 5.0÷5.4.

[0144] The reaction is partially stopped by adding 0.1 Kg 20% sodiumcarbonate as the mixture viscosity achieves a value of 50 mPas.

[0145] After this step, the pH increases again to 6.0÷6.2 and thereaction is continued by loading: 58.1 Kg Urea (molar ratioCH₄N₂O/CH₂O=/1.9).

[0146] The temperature must be brought again to 90° C. and then 0.6 Kg30% Ammonium Sulphate are added to cause the pH to again lower to5.3÷5.7.

[0147] The reaction is monitored as the viscosity of said mixtureachieves a value of 1,000 mPas (stopping viscosity).

[0148] The stopping is achieved by adding 0.6 Kg 30% Soda, therebybringing the mixture to neutrality.

[0149] Then are loaded:

[0150] 15.9 Kg Water

[0151] 176.1 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.1) and the mixture isheld at 60° C. for 40 minutes.

[0152] Then are added:

[0153] 156.8 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.8).

[0154] The mixture is held at 60° C. for 40 minutes, it is then cooledand supplied to the storing tank.

[0155] The finished product contains in total 26.8% Nitrogen

Example No. 8 UF Resin Granulating Test

[0156] The liquid of Example 7 (having a pH=7.5÷8.0 and a viscosity at20° C.=250÷300 mPas) is conveyed to a 100 liter mixer and held underconstant stirring and heated to 40÷50° C., thereby causing its viscosityto be lowered to 60÷70 mPas.

[0157] By a volumetric pump, the mixture is then supplied to thegranulating device; a static mixer arranged on the pumping line providesmixing with the catalyzer (30% Ammonium Sulphate corresponding to 1.33%by weight based on the liquid material) and the mixture pH lowers to5.6÷5.8.

[0158] At the outlet of the granulating device, the granules passthrough a two-net sieve: the finished product being constituted by thefraction from 2.5 to 4.5 mm.

[0159] The finished product, as made, has the following characteristics:Shape White spherical granules; Granulometry 2.5 ÷ 3.0 mm; TotalNitrogen 39.0% minimum; Hot water soluble nitrogen 30% minimum; Granulehardness 3.0 ÷ 3.5 Kg; Friability 0.5% maximum; End moisture 1% maximum;Apparent density ˜0.65 g/cm³; Activity index 55 ÷ 60%; Ureic nitrogen 5%maximum; Packing by heating: it is not packed after 1 month at 70° C. ina thermo- statized stove; Compression packing it is not packed after 1month under a load of 200 g/cm².

Example No. 9 Preparing the Liquid form UP Resin

[0160] Into a steel reactor having a size variable from 10,000 to 60,000liters, including a stirring system and a heating and cooling system,are loaded, under stirring and at atmospheric pressure and roomtemperature, the following raw materials: 80% Formurea  Kg 386.0 WaterKg 17.1 Urea Kg 68.4

[0161] The mixture is heated to 85° C. and 0.2 Kg 50% Sulphamic Acid areadded, to lower the pH to 4.8÷5.2.

[0162] The reaction is stopped by adding 0.3 Kg 30% Soda as a viscosityof 1,000 mPas is achieved, the pH assuming a stable value of 6.8÷7.0.

[0163] The reaction is continued by adding:

[0164] 62.8 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/2.0).

[0165] The temperature is brought again to 90° C., and then 0.3 Kg 30%Ammonium Sulphate are added, thereby the pH returns to 5.7÷6.0.

[0166] The reaction is locked at a viscosity of 1,600 mPas by adding 0.3Kg 30% Soda.

[0167] After stopping the reaction, neutrality conditions are achieved.

[0168] Then are loaded:

[0169] 7.8 Kg Water

[0170] 220.0 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.0) and the mixture isheld at 60° C. for 60 minutes, and then are further added:

[0171] 48.0 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.9).

[0172] The mixture is held at 40° C. for 30 minutes, then it is cooledand 187.9 Kg hydraded Magnesium Sulphate are further added.

[0173] The end or finished product contains 22.8% nitrogen in total and2% Magnesium in total.

[0174] Example No. 10 - UF resin granulating test The liquid of Example9 (having a pH 7.0÷7.5 and a viscosity at 20° C. 800÷1,000 mPas),together with a water soluble blue dyeing or coloring material (fewppm's would be sufficient) is conveyed to a 100 liter mixer, held underconstant stirring and heated to 60÷70° C., thereby lowering the mixtureviscosity to 110÷130 mPas.

[0175] By a volumetric pump, the mixture is then supplied to thegranulating device; a static mixer arranged on the pumping line providesmixing with the catalyzer (55% Phosphoric Acid in a rate of 0.73% byweight based on the liquid as such) and the pH of the mixture lowers to6.0÷6.3.

[0176] At the outlet of the granulating device, the granules areconveyed through a two-net sieve: the fraction from 2.5 to 4.5 mmconstituting the end or finished product.

[0177] The finished or end product characteristics are as statedthereinbelow: Shape Blue spherical granules; Granulometry 2.5 ÷ 3.0 mm;Total Nitrogen 32.0% minimum; Mesoelements 28% Manganese Hot watersoluble nitrogen 22% minimum; Granule hardness 2.0 ÷ 2.5 Kg; Friability1% maximum; End moisture 2.0% maximum; Apparent density ˜0.80 g/cm³;Activity index 40 ÷ 45%; Ureic nitrogen 2% maximum; Packing by heating:it is not packed after 1 month at 70° C. in a thermo- statized stove;Compression packing it is not packed after 1 month under a load of 200g/cm².

Example No. 11 Preparing the Liquid form UF Resin

[0178] Into a steel reactor having a size variable from 10,000 to 60,000liters, including a stirring system and a heating and cooling system,there are loaded, under stirring, at atmospheric pressure and roomtemperature, the following raw materials: 80% Formurea  Kg 438.6 WaterKg 47.7 Urea Kg 55.4

[0179] The mixture is heated to 80° C. and 0.2 Kg 55% Phosphoric Acidare further added to lower the pH to 4.0÷4.4.

[0180] The reaction is stopped at a viscosity of 800 mPas by adding 0.3Kg 24% Ammonia: the pH is brought to 6.0÷6.2 and the reaction iscontinued by loading:

[0181] 43.7 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/2.5).

[0182] The mixture temperature is brought again to 90° C.; and thereaction is stopped as the viscosity achieves, during this step, a valueof 500 mPas.

[0183] The reaction is fully stopped by adding 0.2 Kg 30% Soda, toprovide neutrality conditions.

[0184] Then are loaded:

[0185] 58.2 Kg Water

[0186] 133.3 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.5) and the temperatureof the mixture is brought again to 100° C.

[0187] Then 0.1 Kg 30% Ammonium Sulphate are further added to bring thepH to 6.0÷6.3.

[0188] The reaction is continued for other 20 minutes before stopping itby adding 0.1 Kg 30% Soda.

[0189] Then are added:

[0190] 222.2 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.9).

[0191] The mixture is held at 60° C. for 60 minutes, then it is cooledand supplied to a storing tank.

[0192] The obtained product contains 25.9% Nitrogen.

Example No. 12 UF Resin Granulating Test

[0193] The liquid of Example 11 (having a pH=7.0÷7.5 and a viscosity at20° C.=400÷500 mPas), is supplied to a 100 liter mixer, held underconstant stirring and heated to 50÷60° C., thereby lowering theviscosity thereof to 70÷90 mPas.

[0194] By a volumetric or displacement pump, the mixture is thensupplied to the granulating device; a static mixer arranged on thepumping line provides mixing with the catalyzer (30% Ammonium Sulphatein a rate of 1.66% by weight based on the liquid as such) and the pH ofthe mixture lowers to 5.6÷5.8.

[0195] At the outlet of the granulating device, the granules areconveyed through a two-net sieve: the finished or end product comprisingthe fraction from 2.0 to 4.0 mm.

[0196] The end or finished product has the following characteristics:Shape White spherical granules; Granulometry 2.0 ÷ 2.5 mm; TotalNitrogen 38.0% minimum; Hot water soluble nitrogen 27.5% minimum;Granule hardness 2.0 ÷ 2.5 Kg; Friability 1% maximum; End moisture 1%maximum; Apparent density ˜0.75 g/cm³; Activity index 47 ÷ 53%; Ureicnitrogen 4% maximum; Packing by heating: it is not packed after 1 monthat 70° C. in a thermo- statized stove; Compression packing it is notpacked after 1 month under a load of 200 g/cm².

Example No. 13 Preparing the Liquid form UF Resin

[0197] Into a steel reactor having a size variable from 10,000 to 60,000liters, including a stirring system and a heating and cooling system,there are loaded, under stirring, at atmospheric pressure and roomtemperature, the following raw materials: 70% Formurea  Kg 377.4 WaterKg 16.4 Urea Kg 69.2

[0198] The mixture is heated to 95° C. and 0.6 Kg 30% Ammonium Sulphateare further added to lower the pH to 5.0÷5.5.

[0199] The reaction is stopped at a viscosity of 500 mPas by adding 0.4Kg 24% Ammonia: the pH being brought to 5.8÷6.2.

[0200] The reaction is continued by loading:

[0201] 48.5 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/2.2).

[0202] The temperature of the mixture is brought again to 90° C., andthe reaction is stopped at a viscosity of 1,200 mPas.

[0203] A full stopping of the reaction is achieved by adding 0.5 Kg 30%Soda.

[0204] After stopping the reaction, neutrality conditions are achieved.

[0205] Then are further loaded:

[0206] 115.3 Kg Water

[0207] 103.8 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.4), the mixture beingheld at 50° C. for 50 minutes, and then are further added:

[0208] 247.6 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.75)

[0209] 20.3 Kg hydrated Manganese Sulphate.

[0210] The mixture is-brought again to a temperature of 40° C. for 40minutes and then is cooled and supplied to the storing tank.

[0211] The end or finished product contains 24.8% Nitrogen in total and0.5% Magnese.

Example No. 14 UF Resin Granulating Test

[0212] The liquid of Example 13 (having a pH 7.0 and a viscosity at 20°C.=250÷350 mPas), together with a water soluble violet dyeing material(few ppm's would be sufficient) is conveyed to a 100 liter mixer, heldunder constant stirring and heated to 40÷50° C., thereby lowering themixture viscosity to 60÷70 mPas.

[0213] By a volumetric pump, the mixture is then supplied to thegranulating device; a static mixer arranged on the pumping line providesmixing with the catalyzer (30% Ammonium Sulphate in a rate of 1.0% byweight based on the liquid material as such) and the pH of the mixturelowers to 6.2÷6.4.

[0214] At the outlet of the granulating device, the granules passthrough a two-net sieve: the fraction from 2.0 to 4.0 mm constitutingthe end or finished product.

[0215] The end or finished product, as made, has the followingcharacteristics: Shape Violet spherical granules; Granulometry 2.0 ÷ 2.5mm; Total Nitrogen 38.0% minimum; Microelements 0.75% Manganese Hotwater soluble nitrogen 32% minimum; Granule hardness 2.0 ÷ 2.5 Kg;Friability 1% maximum; End moisture 2.0% maximum; Apparent density ˜0.80g/cm³; Activity index 75 ÷ 80%; Ureic nitrogen 5% maximum; Packing byheating: it is not packed after 1 month at 70° C. in a thermo- statizedstove; Compression packing it is not packed after 1 month under a loadof 200 g/cm².

Example No. 15 Preparing the Liquid form UF Resin

[0216] Into a steel reactor having a size variable from 10,000 to 60,000liters, including a stirring system and a heating and cooling system,there are loaded, under stirring, at atmospheric pressure and roomtemperature, the following raw materials: 43% Formaldehyde Kg 372.0 SodaKg 0.2  Urea Kg 125.0

[0217] (molar ratio CH₄N₂O/CH₂O=1/2.5)

[0218] The mixture is heated to 100° C. and 0.4 Kg 20% Formic Acid arefurther added to lower the pH of the mixture to 4.8÷5.2.

[0219] The temperature of the mixture is held at 100° C. for 50 minutes.

[0220] The reaction is then stopped by adding 0.5 Kg 20% SodiumCarbonate.

[0221] After stopping the reaction, neutrality conditions are achieved.

[0222] Then there are further loaded:

[0223] 88.3 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.5) and the temperatureis held at 75° C. for 30 minutes.

[0224] Then are further added:

[0225] 43.6 Kg Water

[0226] 320.0 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.6).

[0227] The temperature of the mixture is held 40° C. for 60 minutes, andthen the mixture is cooled and are further added:

[0228] 50.0 Kg (II) Iron-EDTA

[0229] The end product contains 24.8% total Nitrogen and 0.8% Iron.

Example No. 16 UF Resin Granulating Test

[0230] The liquid of Example 15 (having a pH=6.5÷7.0 and a viscosity at20° C.=250÷350 mPas), together with a water soluble brown dyeing orcoloring material (few ppm's would be sufficient) is conveyed to a 100liter mixer, held under constant stirring and heated to 40÷50° C. tolower its viscosity to 60÷80 mPas.

[0231] By a volumetric pump, the mixture is then supplied to thegranulating device; a static mixer arranged on the pumping line providesmixing with the catalyzer (20% Formic Acid at a rate of 1.5% by weightbased on the liquid material as such) and the pH of the mixture lowersto 5.6÷5.8.

[0232] At the outlet of the granulating device, the granules areconveyed through a two-net sieve: the finished or end product comprisingthe fraction from 1.5 to 3.5 mm.

[0233] The finished or end product has the following characteristics:Shape Brown spherical granules; Granulometry 1.5 ÷ 2.5 mm; TotalNitrogen 38.0% minimum; Microelements 1.2% Iron; Hot water solublenitrogen 28% minimum; Granule hardness 2.5 ÷ 3.5 Kg; Friability 0.5%maximum; End moisture 2.0% maximum; Apparent density ˜0.85 g/cm³;Activity index 52 ÷ 58%; Ureic nitrogen 5% maximum; Packing by heating:it is not packed after 1 month at 70° C. in a thermo- statized stove;Compression packing it is not packed after 1 month under a load of 200g/cm².

Example No. 17 Preparing the Liquid form UP Resin

[0234] Into a steel reactor having a size variable from 10,000 to 60,000liters, including a stirring system and a heating and cooling system,there are loaded, under stirring, at atmospheric pressure and roomtemperature, the following raw materials: 70% Formurea  Kg 283.0 WaterKg 69.3 Urea Kg 88.2

[0235] The mixture is heated to 90° C. and 0.2 Kg 55% Phosphoric Acidare further added to lower the pH of the mixture to 4.3÷4.8.

[0236] The reaction is locked by adding 0.4 Kg 24% Ammonia as theviscosity of the mixture achieves a value of 200 mPas at 20° C.

[0237] After stopping the reaction, neutrality conditions are achieved.

[0238] Then are further loaded:

[0239] 94.4 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.3) and the temperatureof the mixture is held at 70° C. for 30 minutes.

[0240] Then are further added:

[0241] 195.3 Kg Water

[0242] 169.2 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.75).

[0243] The temperature of the mixture is held at 40° C. for 30 minutes,and then the mixture is cooled and being further added:

[0244] 50.0 Kg Monopotassium Phosphate and 50.0 Kg Di-PotassiumPhosphate.

[0245] The end or finished product contains 18.6% Nitrogen in total, 5%P₂O₅ and 7.5% K₂O.

Example No. 18 UF Resin Granulating Test

[0246] The liquid of Example 17 (having a neutral pH and a viscosity at20° C.=1,000÷1,200 mPas), together with a water soluble red dyeing orcoloring material (few ppm's would be sufficient) is conveyed to a 100liter mixer, held under constant stirring and heated to 60÷70° C., tolower its viscosity to 120÷150 mPas.

[0247] By a volumetric or displacement pump, the mixture is thensupplied to the granulating device; a static mixer arranged on thepumping line provides mixing with the catalyzer (55% Phosphoric Acid ata rate of 1.82% by weight based on the liquid material as such) and thepH of the mixture is lowered 6.5÷6.7.

[0248] At the outlet of the granulating device, the granules areconveyed through a two-net sieve: the end product comprising thefraction from 3.0 to 5.0 mm

[0249] The end or finished product has the following characteristics:Shape Red spherical granules; Granulometry 3.0 ÷ 3.5 mm; Total Nitrogen30.0% minimum; Macroelements 8.0% P₂O₅ and 12.0% K₂O; Hot water solublenitrogen 20% minimum; Granule hardness 1.5 ÷ 2.5 Kg; Friability 1%maximum; End moisture 2.0% maximum; Apparent density ˜0.65 g/cm³;Activity index 40 ÷ 45%; Ureic nitrogen 1% maximum; Packing by heating:it is not packed after 1 month at 70° C. in a thermo- statized stove;Compression packing it is not packed after 1 month under a load of 200g/cm².

Example No. 19 Preparing the Liquid form UF Resin

[0250] Into a steel reactor having a size variable from 10,000 to 60,000liters, including a stirring system and a heating and cooling system,there are loaded, under stirring, at atmospheric pressure and roomtemperature, the following raw materials: 43% Formaldehyde Kg 325.0 SodaKg 0.15  Urea Kg 140.0

[0251] (molar ratio CH₄N₂O/CH₂O=1/2.0)

[0252] The mixture is heated to 98° C. and 0.2 Kg 55% Phosphoric Acidare further added to lower the pH of the mixture to 4.0÷4.5.

[0253] The reaction is topped by adding 0.4 Kg 24% Ammonia as theviscosity of the mixture achieves a value of 120 mPas at 20° C.

[0254] After stopping the reaction, neutrality conditions are achieved.

[0255] Then are further loaded:

[0256] 93.3 Kg Urea (molar ratio CH₄N₂O/CH₂O=1/1.2) and the mixture isheld at 75° C. for 30 minutes.

[0257] Then are further added:

[0258] 180.65 Kg Water

[0259] 166.7 Kg Urea (end molar ratio CH₄N₂O/CH₂O=1/0.7).

[0260] The temperature of the mixture is held at 40° C. for 30 minutes,and then the mixture is cooled and being further added:

[0261] 93.0 Kg Potassium Sulphate.

[0262] The end or finished product contains 18.6% Nitrogen in total and5% K₂O.

Example No. 20 UF Resin Granulating Test

[0263] The liquid of Example 19 (having a pH=7.0÷7.5 and a viscosity at20° C.=950÷1,050 mPas), together with a water soluble green dyeing orcoloring material (few ppm's would be sufficient) is conveyed to a 100liter mixer, held under constant stirring and heated to 60÷70° C.,thereby lowering the mixture viscosity to 120÷140 mPas.

[0264] By a volumetric or displacement pump, the mixture is thensupplied to the granulating device; a static mixer arranged on thepumping line provides mixing with the catalyzer (55% Phosphoric Acid ina rate of 1.45% by weight based on the liquid material as such) and thepH of the mixture lowers to 6.0÷6.2.

[0265] At the outlet of the granulating device, the granules areconveyed through a two-net sieve: the finished or end product comprisingthe fraction from 3.0 to 5.0 mm.

[0266] The end or finished product, as made, has the followingcharacteristics: Shape Green spherical granules; Granulometry 3.0 ÷ 3.5mm; Total Nitrogen 30.0% minimum; Macroelements 8.0% K₂O Hot watersoluble nitrogen 22% minimum; Granule hardness 1.5 ÷ 2.5 Kg; Friability1% maximum; End moisture 2.5% maximum; Apparent density ˜0.90 g/cm³;Activity index 50 ÷ 55%; Ureic nitrogen 1% maximum; Packing by heating:it is not packed after 1 month at 70° C. in a thermo- statized stove;Compression packing it is not packed after 1 month under a load of 200g/cm².

[0267] From the above disclosure it should be apparent that theinvention fully achieves the intended aim and objects.

[0268] In particular, the invention provides a method. for makingnitrogenous and complex fertilizers, slowly releasing nitrogen, andhaving a granule form, allowing to make a very homogeneous product andwhich can accordingly be easily applied by conventional applying meansfor distributing granule form manures.

[0269] The invention as disclosed is susceptible to severalmodifications and variations, all of which will come within theinventive idea scope.

[0270] Moreover, all the constructional details of the disclosed systemcan be replaced by other technically equivalent elements.

[0271] Furthermore, some products or components used for preparing theinventive fertilizer can be replaced by other technically equivalentelements.

1. A method for making a nitrogenous and complex fertilizer, for slowlyreleasing nitrogen, in granule form, wherein said method comprises thesteps of preparing an aqueous urea-formaldehyde dispersion with a molarurea/formaldehyde ratio from 0.8:1 to 2:1, adding to said dispersion anaqueous catalyzer solution in a weight ratio from 0.1 to 4%, controllinga pH of said dispersion to hold said pH within a range from 4.0 to 7.0,and supplying said dispersion to a granulating device, said granulatingdevice including recycling means for recycling a granulated product as agrowth seed.
 2. A method, according to claim 1, wherein said aqueousurea: formaldehyde dispersion has a molar ratio preferably from 1:1 to1.5:1.
 3. A method, according to claim 1, wherein said method comprisesan optional step of adding to said aqueous urea/formaldehyde dispersion,a powder urea/formaldehyde resin optionally as a recycle product, havinga particle size less than 0.5 mm and water to provide a viscosity from40 to 200 mPas at a temperature from 40 to 70° C.
 4. A method accordingto claim 3 wherein said viscosity is from 80 to 120 mPas.
 5. A method,according to claim 1, wherein said acqueous catalyzer solution is addedwith a weight ratio of preferably 0.5 to 2%.
 6. A method, according toclaim 1, wherein said aqueous catalyzer solution is selected from thefollowing catalyzer solutions: 10% Sulphuric Acid, 50% Sulphamic Acis,50% Ammonium Nitrate, 30% Ammonium Sulphate, 20% Ammonium Chloride, 25%Mono-Ammonium Phosphate, 33% Ammonium Acetate, 20% Formic Acid, 17%Hydrochloric Acid, 30% Nitric Acid, 55% Phosphoric Acid, 55% AceticAcid, 30% Ammonium Formate.
 7. A method, according to claim 1, whereinsaid aqueous dispersion has a pH from 5.0 to 6.0.
 8. A method, accordingto claim 1, wherein said formulated product comprises urea/formaldehydegranules having a density in a range from 0.5 to 1 g/cm³.
 9. A method,according to claim 8, wherein said density is from 0.8 to 9 g/cm³.
 10. Amethod, according to claim 8, wherein said granules have a sphericalshape and a diameter from 0.5 to 5 mm.
 11. A method, according to claim8, wherein said granules have a diameter from 2.0 to 4.0 mm.
 12. Amethod, according to claim 1, wherein said method comprises a furtherstep of adding to said aqueous urea/formaldehyde dispersion, macroand/or meso and/or micro-elements.
 13. A method, according to claim 1,wherein said method comprises a further step of adding to said aqueousurea/formaldehyde dispersion potassium, in a chloride, nitrate orsulphate form, to provide a NK fertilizer with a nitrogen contentslarger than or equal to 3% and a potassium contents, expressed as K₂Ogreater than or equal to 5%.
 14. A method, according to claim 1, whereinsaid method comprises a further step of adding to said aqueousurea/formaldehyde dispersion phosphorus in an alkaline metal,earth-alkaline metal or ammonium phosphate or polyphosphate form or asphosphoric or polyphosphoric acids, to provide a NP fertilizer having anitrogen contents greater than or equal to 30% and a phosphoruscontents, expressed as P 0, greater than or equal to 5%.
 15. A methodaccording to claim 1, wherein said method comprises a further step ofadding to said urea/formaldehyde mixture phosphorus in the form ofalkaline, earth-alkaline metals or ammonium phosphate or polyphosphateor phosphoric or polyphosphoric acids, and potassium, such as potassiumchloride, nitrate, sulphate or phosphate, to provide a NPK fertilizerhaving a nitrogen contents greater than or equal 3%, a phosphorouscontents expressed as P₂O₅, greater than or equal to 5%, and a potassiumcontents, expressed as K₂O, grater than or equal to 5%.
 16. A granulatednitrogenous fertilizer, in particular for agricultural use, made by amethod according to claim 1, wherein said nitrogenous fertilizer has atotal nitrogen contents from 36 to 42%.
 17. A fertilizer, according toclaim 16, wherein said total nitrogen contents are preferably from 38 to40% by weight.
 18. A fertilizer according to claim 16, wherein saidfertilizer has a ureic nitrogen contents less than 5% by weight.
 19. Afertilizer, according to claim 16, wherein said fertilizer has a nitricnitrogen contents less than 10% by weight.
 20. A fertilizer, accordingto claim 19 wherein said nitric nitrogen contents are from 2 to 5% byweight.
 21. A fertilizer, according to claim 16, wherein said fertilizerhas an ammoniacal nitrogen contents less than 15% by weight.
 22. Afertilizer, according to claim 21, wherein said ammoniacal nitrogencontents are from 3 to 8% by weight.
 23. A fertilizer, according toclaim 16, wherein said fertilizer comprises the following secondaryelements and/or microelements: sulphur≦30% magnesium≦10% calcium≦10%,boron≦1%, iron≦8%, zinc 5%, manganese≦5%, copper≦5% and molybdenum≦3%.24. A fertilizer, according to claim 16, wherein said fertilizer has anactivity index from 20 to 40, for slowly releasing nitrogen and optionalelements included in said fertilizer.
 25. A fertilizer, according toclaim 24, wherein said activity index is from 40 to
 60. 26. Afertilizer, according to claim 24, wherein said activity index is from60 to 80, for quickly releasing nitrogen and optional elements includedin said fertilizer.
 27. A fertilizer, according to claim 16, whereinsaid fertilizer comprises spherical granules having a diameter from 0.5to 5 mm.
 28. A fertilizer, according to claim 27, wherein said sphericalgranules have a diameter from 2 to 3 mm.
 29. A fertilizer, according toclaim 16, wherein said fertilizer comprises granules having a hardnessfrom 1 to 5 Kg.
 30. A fertilizer, according to claim 29, wherein saidgranules have a hardness from 2 to 3 kg.
 31. A fertilizer, according toclaim 16, wherein said fertilizer comprises granules having a friabilityless than or equal to 1%.
 32. A fertilizer, according to claim 27,wherein said spherical granules do not have any trend to packing, evenif said granules are held in dry conditions at a temperature of 70° C.for a period of a month.
 33. A fertilizer, according to claim 27,wherein said spherical granules do not have any trend to packing even ifsaid granules are subjected, for ten days, to a pressure of 200 g/cm² ata temperature of 38° C.